LTE (Long Term Evolution) system adopts HARQ (Hybrid Auto Repeat Request) to improve the reliability of data transmission. When downlink HARQ function is enabled, terminal equipment decodes the downlink data package received. ACK (ACKnowledgement) will be fed back to base station if the decoding is correct, while NACK (Negative ACKnowledgement) will be fed back for requiring base station re-transmitting the data package if it fails.
For LTE multi-carrier system, to support the system bandwidth wider than LTE system, such as 100 MHz, a kind of frequency spectrum capable of directly distributing 100 M bandwidth, as shown in FIG. 1; a kind to aggregate the frequency spectrum distributed for current system and merge into big bandwidth to supply for the use of LTE multi-carrier system. Then the uplink and downlink carriers in the system can be configured asymmetrically, viz. user may occupy N≧1 carriers for downlink transmission and M≧1 carriers for uplink transmission, as shown in FIG. 2.
It is specified in the available standard that each carrier has independent HARQ process, viz. one transport block (TB) can only be transmitted on one carrier. When base station and terminal equipment occupy several carriers to transmit data, each carrier transmits different TB respectively.
Therein, for HARQ, under single codeword transmission mode, each process comprises one TB, while under multiple codeword transmission mode, each process comprises two TBs.
After HARQ function is enabled, the receiving end will store the TB with decoding failure in the buffer, and then decode after merging it with the version re-transmitted by the sending end.
LTE Rel-10 system specifies eight terminal equipments with different capability levels, which can support various bandwidth and buffer sizes. The higher level the terminal equipment is, the greater the corresponding buffer is. All these eight terminal equipments of different capability levels can support carrier aggregation (CA), under the premise that the total bandwidth after aggregation is not more than their processing capability.
In the procedure of realizing the embodiments of the present invention, at least the following problems existing in the current technologies were found:
In CA system, concurrent HARQ processes undergoes linear increase along with the number of aggregated carrier, and the TB numbers to be stored by corresponding receiving end increase linearly as well; however the maximum bit of each TB must be less than the maximum bit of each TB supported by terminal equipment. If the storage is classified and HARQ process is stored by following the method of LTE Rel-8, the buffer space corresponding to each TB will be greater than its maximum demand, thus causing buffer waste; on the other hand, as the concurrent HARQ process in the system increases but the maximum number of HARQ process stored in the buffer remains unchanged, it means the subsequent HARQ processes cannot be stored when the number of wrong HARQ processes exceed the upper limit of buffer, hence only ARQ (Auto Repeat Request) function can be realized, viz. merge gain of re-transmission cannot be obtained.